Reactions between organic nitrogen compounds and reaction products of formaldehyde with sulphamates



Patented Feb. 13, 1945 2,369,503 REACTIONS BETWEEN ORGANIC NITROGEN COMPOUNDS AND REACTION PRODUCTS OF FORMALDEHYDE WITH SULPHAMATES Joseph Frederic Walker, Lewiston, N. Y., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware I No Drawing. Application March 12, 1941,

, Serial No. 882,944 I h 4 Claims. This invention, relates to reactions involvin formaldehyde derivatives of sulphamic acid salts and organic nitrogen compounds, particularly nitrogen compounds having a reactive hydrogen atom directly attached to a nitrogen atom, and to products resulting from such reactions.

Reactions of formaldehyde with organic amino, amido or imido compounds are widely used to prepare products which have found extensive commercial applications. Among the compounds so reacted with formaldehyde are urea, thiourea and the like, melamine, and various proteins derived from both animal and vegetable sources. The present invention is concerned with reactions involving similar organic nitrogen-containing substances, employing in place of formaldehyde, reaction products of formaldehyde with sulphamic acid salts. Y I

It is an object of the present invention to provide a method of reacting certain formaldehyde derivatives of sulphamic acid, with organic nitrogen-containing substances, especially proteins and the like substances. A further object is to provide useful products which products result from the reactions with which the present method is concerned. These and still further objects will be apparent from the following description of the invention.

The above objects may be accomplished in accordance with the present invention by reacting a formaldehyde derivative of a salt of sulphamic acid, or of a substituted sulphamic acid, which derivative has been prepared under alkaline conditions, with an organic nitrogen-containing material having a reactive hydrogen atom directly attached to a'nitrogen atom. It has been discovered that such reactions may be carried out in a practical manner to yield valuable products, which products appear to be true reaction products of the two reactants and not merely reaction products of formaldehyde with the nitrogencontaining compound.

The formaldehyde derivatives which are useful in practicing this invention are those which have been prepared by reacting formaldehyde under alkaline conditions with a salt of sulphamic acid, or with a salt of a substituted sulphamic acid wherein one amino hydrogen atom of the sulphamic acid residue has been replaced by a hydrocarbon radical such as an alkyl, aryl, aralkyl or cycloparaflinic group. Thus formaldehyde reacti n products with sulphamic acid salts of alkali metals, ammonia, amines. alkylol amines and the alkaline earth metals, which reaction products have been prepared under alkaline conditions,

m'ay beused. Particularly useful are the reaction .products of formaldehyde with alkaline earth metal sulphamates. especially calcium sulphamate, which are prepared by reacting formaldehyde with the sulphamate under alkaline conditions, e. g. at a pH of 8 to 10, as described in my copending application Serial No. 358,521, filed September 26, 1940, now Patent No. 2,321,958. The term "alkaline earth metals" is used to include magnesium, along with metals such as calcium, strontium, and barium. In preparing formaldehyde-sulphamate reaction products for use in practicing the present invention, the reaction between formaldehyde and the sulphamate should be effected under distinctly alkaline conditions. However, too strongly alkaline conditions, i. e. reaction media having a pH higher than about 11, are not recommended, and in general reaction media having a pH of 8 to 10 give best results. The reactants will generally be employed in 'stoichiometrical proportionate, 1 mole of formaldehyde for each sulphamic acid residue .in the Y sulphamate, although an excess of either reactant may be used.

A copending application by Martin E. Cupery, Serial No. 382,338, filed March 8, 1941, is concerned with reactions involving organic nitrogencontaining substances of the type here concerned and formaldehyde-sulphamate reaction products,

in general. Formaldehyde may be reacted with sulphamates under either acidic or alkaline conditions, but the exact chemical structures of the reaction products obtained are not definitely known. It is believed that those products prepared under acidic conditions are methylene sulphamat'es, or hydrates thereof, while those prepared under alkaline conditions are true methylol compounds. At any rate, products prepared under alkaline conditions are distinct from corresponding products prepared under acidic conditions in several important respects. Thus the formaldehyde-calcium sulphamate reaction product prepared in a medium having a pH of 8 to 10 is very soluble, 1 gram of water dissolving about two parts ofthe product. Furthermore, the dried product is stable and solutions thereof are reasonably stable for considerable time if buffered at a pH of 8 to 10. In contrast, product obtained by reaction in a medium which is acidic, is somewhat less stable and much less soluble in The higher stability and much greater solubility, particularly of alkaline earth sulphamate products, when prepared under alkaline conditions, render them especially effective for uses involving reactions with organic nitrogencontaining substances of the type hereinafter defined.

The organic nitrogen-containing substances which may be reacted with the above formaldehyde derivatives iii-accordance with the present invention are those which contain at least one reactive hydrogen atom directly attached to a nitrogen atom of the molecule. Thus, organic substances or compounds which contain an amino, amido, vor imido group may be used. Specific examples of such substances are methyl, dimethyl, dipropyl, phenyl methyl and other allphatic and aromatic primary and secondary amines; melamine, formamlde, acetamlde, urea, urea-formaldehyde reaction products, e. g., meth ylol ureas and resins, thiourea, and the like; and proteins and protein-like material such as gelatin, glue, casein, soya bean protein, zein, powdered blood, hide powder and the like. Such animal products as hides, flesh, fur, wool, etc., which contain substantial quantities of proteins are-also included.

Reaction between the formaldehyde derivative and the organic nitrogen containing material may be effected by mixing together the two reactants in the solid state and'then subjecting the mixture io'heat, under pressureif desired. They may also be reacted in solution, or in the case of a solid nitrogen-containing material such as a molded protein article, such a material may be contacted with a solution of the formaldehyde sulphamate derivative under conditions suitable for effecting the desired reaction.

The following examples are illustrative of the invention.

' Example 1 Three gram samples of fresh, chopped beef were place in open bottles. To one bottle was added cc. of water, to another 20 cc. of a 1% aqueous solution of a formaldehyde-calcium sulphamate reaction product prepared under alkaline conditions, and to the third bottle was added 20 cc. of a 1% aqueous solution of formaldehyde. The bottles were placed in a warm room Example 2 Twenty grams of rennet casein were thoroughly moistened with 5 grams of water and 3 ms of a 45% methanol solution of a reaction product of calcium sulphamate with formaldehyde, which reaction product had been prepared under alkaline conditions. This mixture was then placed in a compression mold and heated under a pressure of 4,000 lbs. per sq. inch at approximately 160 C. for 15 minutes. On cooling, a clear, translucent, homogeneous molding was obtained. The product upon removal from the mold was somewhat plastic and could be easily cut with a knife. After standing for several hours, it became hard and tough. The material did not crack or check on storage and. was not disintegrated on prolonged soaking in water. A blank sample obtained from a similar casein charge moistened with 8 grams of water did not set up in the mold and considerable extrusion took place when pressure was applied. The product, through clear and translucent, gradually disintegrated on soaking in water and checked and cracked on storage.

Example 3 Ten grams of rennet casein were moistened with a solution of 0.5 gram of a calcium sulphamate-formaldehyde reaction product, prepared under alkaline conditions, dissolved in 4 cc. of

water. This mixture was then compressed for 15 minutes at 125 C. under a pressure of 2,000 lbs per sq. inch. The molded chip prepared in this way showed no change of dimensionskafter-lsoaking in water for eight days.

Molded casein products similar in properties to those of the product of Example 3 were prepared by the method of Example 3 using reaction prod-' ucts, prepared under alkaline conditions, of formaldehyde with magnesium and strontium sulphamates.

Example 4 of the unmodified glue and was superior to glue modified with paraformaldehyde alone. On ,soaking in water for one week, the joints bonded with the modified glue were still intact and possessed a fair degree of strength whereas the joints bonded with unmodified glue had soaked apart. Good results were also obtained when the joints were cold pressed at 200 lbs. pressure.

Example 5 40 under alkaline conditions. ,On standing at room temperature this solution became viscous and gelled in 8 to 12 days. Such a composition may be used for coating and impregnating purposes.

Example 6 A protein paint was prepared by dispersing soya bean alpha-protein in water by means of caustic soda and boric acid. A small amount of a softening agent was added, a commercial grade or coating clay was dispersed throughout the mixture,

' and then there was added a calcium sulphamateformaldehyde reaction product, prepared under alkaline conditions, in an amount corresponding to 10% by weight. based on the weight of the protein present. The weight percentages of protein and clay in the final composition were 6.3 and 41% respectively.

The calcium sulphamate-formaldehyde product was an excellent insolubilizer for the protein in the above paint composition. The composition did not gel even after standing for three weeks at room temperature. When applied to a wall paper base, followed by drying, the composition yielded an excellent water-resistant coating. Although drying the coated sheet at ordinary temperature gave a paper having definite water resistance, subjection of the coated paper to a final calendering treatment at elevated temperature or to a baking treatment, e. g. at to C.for 0.5 hour, markedly increased water resistance, and such after-treatment is preferred. Coated paper prepared using the above paint composition was distinctly more wator-resistant than coated paper prepared under the same conditions using the same type of coat- There resulted a clear, water-soluble resin.

asoaoos ing composition except that it contained parai'ormaldehyde in place of the calcium sulphamate-formaldehyde reaction product. Furthermore, the composition containing paraformaldehyde had an objectionable odor of formaldehyde and set to a gel upon standing for fourto twentyfour hours. n Such rapid gelling of compositions containing paraformaldehyde is disadvantageous in that it necessitates using the paint within a relatively short time after preparation. On the other hand, a composition such as'that described above may be stored afterpreparation for as long as three weeks without gelling taking place.

,E'zample 7 .and a clear translucent product was obtained.

The unmodified protein did not set up in casting and most of it extruded from the mold. The modified casting did not check on aging, whereas the control showed pronounced checking.

I Example. 8

A reaction product of formaldehyde with cal cium sulphamate, prepared at a pH of 8-10, and isolated in solid form, was reacted with urea by heating the reactants in an aqueous solution. On boiling down, the solution of resin became extremely viscous and finally hardened to a colorless, glass-like solid. In another experiment equimolar quantities of the same two reactants were heated with a small amount of water. The product obtained was an effective adhesive for wood.

- Example 9 Equimolar quantities of melamine and a calcium sulphamate-formaldehyde reaction product prepared under alkaline conditions employing two mols of formaldehyde per mol of sulphamate were dissolved in a small amount of water. On gently heating the resulting solution, it was concentrated to a'clear water-soluble resin.

Although the reactions with nitrogen-containing compounds with which the present invention is concerned may be carried out under either alkaline or acidic conditions, it is preferred to effect such reactions ,under substantially neutral or alkaline conditions, e. g., at a pH of about 6-12, preferably 8-10. This is particularly true when the reactions are carried out in solution. In the case of reactions involving protein materials, acidic conditions should be avoided as much as possible in order to prevent undue degradation of the protein. The reactions may be effected merely by permitting the reactants to stand in contact with each other at room temperatures for a sufficient period of time or they may be actively promoted by the application of heat. Temperatures above room temperature and as high as about 200 C. are suitable for so promoting the reaction. Ordinarily, temperatures within the range of from 80-110" C. are preferred, since at such temperatures there is little tendency for degradation of products such as proteins to occur. x

Compositions, either solid or liquid, which contain products prepared in accordanceiavith this invention, may also contain such substances as iillers,'softenins agents, modifieraandthe like which find wide use in preparing-similar compositions containing reaction products of formaldehyde with proteins, urea, etc.

While any formaldehyde-sulphamate reaction product which has been prepared under alkaline conditions may be used for the present purpose, the products from alkaline earth metal sulphamates, and particularly from calcium sulphamate, are especially well suited. They are much more stable than derivatives from, for example,

-. the alkali metal sulphamates, and are characterized by an unusually high solubility.-- Thus calcium sulphamate is soluble to the extent of two parts in one part by weight of water even at ordinary temperatures. Furthermore, it is stable over long periods of time in the dry state if stored under anhydrous conditions, particularly if admixed with a small amount of a suitable alkaline buffer compound. In contrast, products prepared from alkali metals are relatively unstable in the solid state, but may be used for the 1 present purpose soon after preparation, or the reaction media in which they are prepared may be used directly without first isolating the formaldehyde-sulphamate reaction product.

In practicing the invention it is not necessary that a preformed formaldehyde-sulphamate reaction product be employed, since good results may be obtained by adding formaldehydeand the sulphamate to the organic nitrogen-containing material. Under such conditions the action of formaldehyde upon, for example, a protein is substantially modified by the presence of the sulphamate. A probable explanation of this fact is that there first occurs a reaction between the formaldehyde and the sulphamate to form a reaction product thereof, which reaction product then further reacts with the protein. However, it may be that all three materials react simultaneously .with each other. It is to be understood that any combination of reagents which would lead to the formation of a reaction product of formaldehyde with a sulphamate under alkaline conditions in the pres- The present invention may be practiced employi-ng various amounts of the formaldehydesulphamate derivative. In general when the reaction involves a protein material or composition, it is preferred to employ in the neighborhood of 1 to 25% by weight of the formaldehyde derivative. based on the protein. Larger amounts may be used if desired, especially in the case of reactions involving such substances as. urea and the like, in which case equimolar amounts of the reactants will generally be used, although an ex- If desired formaldehyde-sulphamate derivative.

Reactions between the nitrogen-containing compounds of the type herewith concerned and formaldehyde-sulphamate products, appear to involve the latter compounds as such and not merely I formaldehyde which has been liberated therefrom. This appears to be the case especially when reaction with the nitrogen-containing compound is carried out under alkaline conditions. The nature of the reactions involved is not clear but indications are that the formaldehyde-sulphamate products act as cross-linking agents. They apparently do not function merely as agents for liberating formaldehyde in the reaction media since the odor of formaldehyde is usually not apparent during reactions with the nitrogen compounds. This is almost ex-clusively the case when the reactions are effected under alkaline conditions. When reaction with the nitrogen-containing compound is effected under slightly acidic conditions, there may be a tendency for some formaldehyde to be liberated, but it is believed that in general the formaldehyde-sulphamate product reacts as an entity, even under slightly acidic conditions.

One advantage in using, for example, the formaldehyde derivative of calcium sulphamate or other similar formaldehyde derivatives as protein modifying agents is that such a compound possesses no formaldehyde odor. Ordinarily formaldehyde, or such other protein modifiers which evolve free formaldehyde during use, are quite objectionable due to the irritating nature of the evolved formaldehyde vapors. When using the present formaldehyde derivatives, especially under alkaline conditions, the odor of formaldehyde is usually not detectable even when, for example, the protein composition to which has been added substantial amounts of the formaldehyde derivative is heated atelevated temperatures. A further advantage attending the use of the present formaldehyde derivatives i that solutions thereof have comparatively little tanning action upon the human skin at ordinary temperatures. In contrast, formaldehyde is known to have an objectionable tanning action upon the hands of workers handling it.

The high solubility of the present formaldehyde-sulphamate reaction products facilitates the preparation of homogeneous protein compositions containing the same, thu making it possible to bring about complete reaction of all of the sulphamate derivative with all of the protein. Paraformaldehyde has been used for insolubilizing glue and similar proteins, but due to its insolubility in compositions of such materials, such use of paraformaldehyde has been limited. Because of its limited solubility it is practically impossible to distribute paraformaldehyde uniformly throughout a protein composition before hardening occurs, the result being that reaction with the protein is not uniform throughout. In contrast,

the present formaldehyde sulphamate derivatives prepared under alkaline conditions are readily dispersed, throughout aqueous protein compositions, insuring uniform reaction.

Formaledhyde reacts almost instantaneously with proteins, while the present formaldehyde derivatives generally react more slowly so that better control of reactions is possible. Thus a hot compression molding prepared from rennet casein moistened with ordinary formaldehyde solution is a loose conglomerate of insolubilized granules. In contrast,'molded products obtained in Examples 2, 3, and 7 are homogeneous throughout and generally clear, translucent, and strong, since insolubilization of the protein by the present method does not take place until the protein has melted or dissolved.

By controlling the alkalinity of the reaction mixtures, controlled insolubilization or modification of proteins by means of the present formaldehyde derivatives is possible. This is particularly true when the reactions involved are carried out at substantially neutral or alkaline conditions. This is distinctly advantageous. When using formaldehyde as a protein hardening agent, it is generally considered that the use of an acid such as oxalic acid or the like is necessary to inhibit the .action of theformaldehyde or paraformaldehyde. However, since solutions or dispersions of proteins such as casein and soya bean proteins are formed under substantially neutral or alkaline conditions the addition of an acid to such a composition will tend to precipitate a certain amount of the protein. The precipitated material is generally in the form of a powder having little water resistance, even though the individual particles have been insolubilized by the action of formaldehyde. When using formaldehyde-sulphamate derivatives in accordance with the present invention, it is not necessary to employ an acid to inhibit action on the protein, and such derivatives in general react relatively slowly and cause the formation of a continuous water-resistant gel which leaves a resinous water-resistant layer or fllm upon evaporation.

' As many different modifications of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited to the details of the foregoing description and examples, which are intended to be illustrative only, except as in dicated in the appended claims.

I claim:

1. The method which comprises bringing into contact at reaction temperature a protein and a formaldehyde derivative of a sulphamic acid salt, said derivative having been prepared by reacting formaldehyde with said salt-under alkaline conditions.

2. The method which comprises bringing into contact at reaction temperature a protein and a formaldehyde derivative of calcium sulphamate,

said derivative having been prepared by reacting formaldehyde with said sulphamate under alkaacid salt, said derivative having been prepared under alkaline conditions.

' JOSEPH FREDERIC WALKER. 

